Process and apparatus for producing metallic coatings on various articles



H. SCHNEIDER Nov. 8, 1938.

PROCESS AND APPARATUS FOR PRODUCING METALLIC COATINGS ON VARICUSARTICLES Filed May 3, 1955 INVENTOR. t'a/ns Schneider BY amuwzg wATTORNEY.

Patented Nov. 8, 1938 PATENT OFFICE PROCESS AND APPARATUS FOR PRODUC-ING METALLIC COATINGS narrows 0N vanrous Hans Schneider, rm Cheater, N.Y., assignor to Metal Forming a Coating, Inc.,'a corporation of New YorkApplication May 3, 1935, Serial No. 19,564 5 Claims. (01. 91-122) Myinvention relates to a process and apparatus for producing a metalliccoating, particularly a silver coating on various articles, metallic ornon-metallic.

In the prior art where the solutions were blown in separate mists fromthe nozzle and mixed in midair, considerable portions of the solutionsnever came into contact for their chemical reaction before they reachedthe article to be coated.

Further in the prior art, where the solutions were subjected to an airjet whether mixed before leaving the nozzle or not, they reached thearticle in the form of a mist. This interfered with good results,particularly in coating the molds used in electrotyping, where there aremany fine cracks and crevices. I have found that better results areobtained wherethe mixed solutions are blown at the article in as nearlyan unbroken stream as possible or in large fragments of the stream asopposed to a mist. The impact against the article is far greater wherethe liquid is thrown at it by the air jet in comparatively large massesthan where blown as a fine spray or mist. The large impact obtained inmy invention is very effective in producing a good coating. It removesair bubbles and enters fine cracks and deep crevices.

It is an object of my invention to mix the solu tions in substantiallyunbroken stream form after leaving the nozzle. It is a further object toblow a stream of mixedsolutions with as little breakingup as possiblewith considerable force against thearticle to be coated. I

My process and apparatus are economical in the use of the reagents aslarge fragments of liquid are thrown directly at the work instead of thereagents being scattered in. a mist, only a part of which settles uponthe work.

Some of the matter disclosed herein formed part of my abandonedapplication Serial No. 592,092, filed February 10,- 1932.

Other objects and advantages will become apparent upon a further studyof the description and drawing, in which:-

Fig. 1 is a diagrammatic view of an apparatus for carrying out myinvention, the nozzle being shown in section, and

Fig. 2 is an end elevation of the nozzle shown by itself.

The apparatus and process will first be de-,

scribed as used in coating an article with silver.

A container 3 is used to hold a solution of silver nitrate. Thecontainer 4 is used to hold a'formaldehyde solution. Leading fromcontainer 3 is a tube 5 which is connected to passage 6 in the nozzle orsupporting member 1. Leading out from the forward end of passage 6 is abent pipe ii having a reduced front orifice. From container 4, anothertube 8 leads to passage 9 of nozzle 1. Leading out from the forward endofpassage 9 is a bent pipe I!) having a reduced front orifice. Pipes l0and II incline forwardly beyond nozzle 1 and converge toward each otherwith their front orifices so aimed that streams the front of nozzle 1and so aimed that the issu--' ing air jet 30 strikes the meeting placefrom behind the streams caused to issue from pipes l0 and II. The frontof nipple I l is some distance to the rear of the orifices of pipes l0and H. Nipple l4 and pipes l0 and H are preferably so aimed with respectto one another, that the streams issuing from said pipes have equalinclinations to air jet 30.

A passage i5 leads from air-passage i3 and extends to the rear of nozzle1 where it joins with tube It. The lower end of tube I 6 is providedwith two branches, one branch I1 leading to container 3 and the otherbranch l8 leading to container 4. A short tube [9 leads from branch l1through stopper 20 into the inside of container 3, while a short tube 2|leads from branch l8 through stopper 22 into the inside of container 4.A tube 23, leading from the bottom of tube 5, extends through stopper2!! to a point near the bottom of container 3, while a tube 24, leadingfrom the bottom of tube 8, extends through stopper 22 to a point nearthe bottom of container 4. Valves 25 and 21 may be provided to regulatethe .flow of solutions through tubes 5 and 8. A valve 26 is provided toregulate the flow of air from air ,line l2. Valves 25 and 21 may beplaced on to nipple I, also branches oil into passage I5 passing throughtube l6, through branches l1 and I8, and tubes I 8 and 2| intocontainers 3 and 4, causing pressure on the top of the liquids held insaid containers. Said pressure forces the silver nitrate solution uptube 23, through tube 5, passage 6 and out the orifice of pipe I I.Similarly, the formaldehyde solution is forced up through tube 24,through tube 8, passage 9 and out the orifice of pipe ll). Pipes I0 andH are aimed to have their issuing streams of solutions meet at a placealong the longitudinal axis of air jet 30, the inclinations of saidstreams to said axis being equal. The apparatus is so proportioned thatthe streams issuing from pipes l0 and H may be equal in velocity and inthe quantity of liquid delivered per second. Adjustment of valves 25 and21 are helpful in maintaining these conditions, although said valves maybe omitted if the parts are carefully proportioned. It is desirable touse as few valves as possible on the solution lines as the former tendto clog and thereby interfere with the operation.

The conditions for maximum efficiency of my process are to have the twostreams issue from pipes l0 and l I at equal velocities, in equalquantitles at equal inclinations to the longitudinal axis of air jet 30and to meet at a place along said axis. With these conditions fulfilled,the streams will coalesce and produce a resultant stream 28 having alongitudinal axis coincident with the longitudinal axis of said jet fora substantial distance beyond the place of meeting. Actually, a certainamount of variation will occur and a certain amount of splashing willtake place at the meeting of the streams.

Coming from behind the place of meeting of the streams, which place isthe origin 29 ofv resultant stream 28, and blowing in the same directionas the resultant stream, air jet 3!! blows said resultant stream forwardsubstantially en masse or, at the worst, in large fragments thereofinstead of breaking it up into a mist. Air jet 30 causes the place ofmeeting 29 of the issuing streams to be on the longitudinal axis of saidjet forward of where it would occur were there no air jet.

The air jet 30 is regulated in intensity to have suflicient strength toblow the resultant stream at the work with substantial force, but yetwith insufficient strength to convert the issuing streams into a mistand with insufficient strength to prevent their meeting. The spacing ofthe forward end of nipple H a substantial distance to the rear of theforward orifices of pipes l0 and I I softens the effect of air jet 30upon the issuing streams, helping to prevent the formation of a mist andto allow the issuing streams to meet.

When air line I2 is closed off by valve 26, the pressure is relieved incontainers 3 and 4 by the escape of the air from said containers throughtube I6, passages l5 and I3 and out nipple 14, allowing the liquids intubes 5 and 8 and passages 6 and 9 to return to their respectivecontainers by gravity and siphoning, preventing thereby loss of theseliquids when nozzle I is handled, and the apparatus is not in use.

Means for heating the solutions are not shown as this can be readilyprovided for by those skilled in the art.

If desired, another container, not shown, for a third solution may beused, said container bein connected to air tube It and having a tube,similar to tube 8,"lea ding therefrom to another passage to beprovided'in nozzle 1, and Having another bent pipe similar to pipes l0and H and aimed to have its issuing stream strike the place of meetingof the other two.

In carrying out my invention for producing a silver coating, I prefer touse a silver nitrate solution consisting of 16 grams of silver nitrateper 1 gallon of' water, and a formaldehyde solution consisting of 2'76cc. of formaldehyde per 1 gallon of water. However, I have found thatthe percentage of silver nitrate per gallon of water may be varied from10 to 30 grams, and still produce good results. I have also found that Imay successfully use to 510 cc. of formaldehyde per gallon of water. Asnoted above, I apply these solutions in equal parts. As is well known inwith tin chloride. Instead of using formaldehyde as a reducing agent, asis well known in the art, Rochelle salts may be used instead. Ammoniumsilver nitrate solution may also be substituted for the silver nitratesolution.

Deposits of other metals besides silver may be done according to myinvention. For making copper deposits, I prefer to use a solution of20%- 50% hydrazene hydroxide and a solution of dilute copper sulphate.For making lead deposits, I

prefer to use a solution of dilute thiocarbamide mixed with 2% of leadacetate and a 5% solution of ammonium hydroxide. For depositing gold, Iprefer to use a l solution of gold chloride and a solution consisting ofa mixture of 50% glycerin and 5% sodium hydroxide with traces of manniteas an accelerator.

Generically speaking, the pipes l0 and II, and the passages 6, I, '9 andIS, with their enclosing walls, are conduits supported by the nozzle ormember I.

The terms liquid form or liquid are used the art, the article to becoated may first be coated I in the claims in the sense as opposed tomist or the mixed streams to strikethe object to be coated, the generaldirection of the mixed streams and the jet being the same, the solutionscontaining metallic and reducing compounds capable of reactingchemically 'upon the mixing of the solutions, to deposit the metal ofthe metallic compound as a coating on the object, the air jet impingingupon the streams with force restricted to hinder the formation of mistbut suilicient to throw the mixture of the streams with considerableforce in relatively large liquid masses upon the object.

2. In the art of coating objects with silver, the process which consistsin forming two streams in liquid form, one a solution of a silvercompound and the other a solution of a reducing agent therefor, mixingthe streams by causing them to meet in liquid form in midair, anddirecting a jet of air against the mixed streams causing the mixture tobe thrown against the object to be coated, whereby a silver coating isdeposited upon said object, the air jet impinging upon the mixture withforce restricted to keep down the formation. of mist but suflicient tothrow the mixture with considerable force in comparatively large liquidmasses upon the object.

3. Apparatus for coating objects with metal comprising a pair ofconduits, a member for supporting said conduits, said conduits extendingbeyond the front of the supporting member, means connected to saidconduits for sending without substantial formation of mist a solution ofa metallic compound through one conduit and a reducing solution thereforthrough the other, said conduits discharging their solutions in liquidform in streams directed to meet and mix in midair, and means upon saidmember for directing a current of air at the mixed streams from the rearof the meeting place of the streams with the force of the currentrestricted to keep down the formation of mist, for throwing the mixturein liquid form upon the object to be coated for depositing a metalliccoating thereon.

4. Apparatus for coating objects with silver comprising a nozzle havingtwo passages therethrough, means connected to said passages for sendinga solution of a silver compound through one passage, and a solution of areducing compound therefor through the other, a pipe-leading out fromthe front of each of said passages directing the streams of thesolutions issuing therefrom to meet in midair, said nozzle having athird passage therethrough, means for sending air under pressure throughsaid third passage to discharge at its forward end, and means at theforward end of the third passage, but at a substantil distance to therear of the meeting place of the streams, for directing the issuing airat said meeting place for throwing the mixed streams upon the object tobe coated for depositing a silver coating thereon.

5. In the art of coating objects with metal, the process which includesforming two unsupported liquid streams of different solutions, directingthem to meet in midair at an angle less than 180 degrees and mix inliquid form, and directing a jet of air against the meeting place of thestreams from substantially within said angle and along a planeintersecting both streams, each stream making the same angle with thejet, said jet impinging upon the streams with force restricted to keepdown the formation of mist and to permit the meeting of the streams, butsuflicient to throw the mixture of the streams with considerable forcein comparatively large liquid masses upon the object, one of saidsolutions containing a metallic compound and the other containingmaterial capable of reacting chemically with the metallic compound toform a coating of the metal on the object.

HANS SCHNEDER.

